This application relates to a refrigerant system having multiple circuits, and a single economizer heat exchanger utilized by at least two circuits.
Refrigerant cycles are utilized to provide cooling and/or heating, refrigeration, etc. As known, in a refrigerant cycle, a refrigerant is compressed at a compressor and then moved to a condenser. From the condenser, the refrigerant passes to an expansion device, and then to an evaporator. From the evaporator, the refrigerant returns to the compressor.
With varying challenges upon a refrigerant cycle, modifications such as the use of multiple circuits have been developed. A multiple circuit system may include two complete and separate cycles of each of the basic components described above. The cycles may be used alternatively or in combination dependent upon the load on the system.
One other aspect that has been recently developed and added to modem refrigerant cycles is an economizer cycle. In an economizer cycle, a portion of the refrigerant downstream of the condenser is tapped and passed through an expansion device. The tapped refrigerant is cooled after having passes through its expansion device, and is then passed through an economizer heat exchanger. The main refrigerant flow downstream of the condenser also passes through the economizer heat exchanger, preferably in a counter-flow arrangement, and is cooled by the tapped refrigerant. This cooling brings the main flow to a somewhat lower temperature than it was previously achieved in the condenser, thus providing a higher cooling capacity when the main flow reaches the evaporator.
The use of an economizer cycle provides benefits that relate to enhanced performance in providing the highest cooling capacity and efficiency under high load conditions. However, in many applications, the addition of an economizer cycle is too expensive to justify its inclusion in a refrigerant cycle. The economizer cycle requires a good deal of additional plumbing, a separate additional heat exchanger, a separate additional expansion valve, piping to both control the tapped refrigerant, re-routing it back to the compressor after passing through the economizer heat exchanger, and modifications in the design of the economized compressors. Thus, while economizers have value in increasing efficiency, in many applications they are too expensive to be adopted. This is particularly true in the above-described multiple circuit systems where all of the additional costs would be multiplied by the number of circuits.
The present invention provides a unique way of lowering the cost of adding an economizer cycle to a multiple circuit refrigerant system as well as further enhancing system performance.